Science helps craft the perfect mac and cheese

In this image taken on April 22, 2013, modernist mac and cheese is shown served in a bowl in Concord, N.H. (AP Photo/Matthew Mead)

By SCOTT HEIMENDINGER -
The Associated Press

Imagine your favorite cheese: perhaps an aged, sharp cheddar, or maybe a blue Gorgonzola or a gentle Monterey Jack. Wouldn't it be wonderful to use those really good cheeses you love on nachos or as a sauce on macaroni or steamed vegetables?

But if you have ever tried melting high-quality cheeses, you've experienced the problem: the cheese separates into a greasy oil slick that no amount of stirring will restore.

One traditional workaround is to make a Mornay sauce, which combines the cheese with a cooked mixture of flour, butter and milk. But a Mornay sauce can end up tasting as much of cooked flour as it does of cheese. The starch in the flour actually masks some of the flavors in the cheese, so the sauce loses its vibrancy.

A clever Canadian-born cheesemaker in Chicago discovered a much better solution around 1912. His name may ring a bell — James L. Kraft.

Kraft found that adding a small amount of sodium phosphate to the cheese as it melted kept it from turning into a clumpy mess of cheese solids swimming in a pool of oil. Kraft patented his invention and used it to make canned, shelf-stable cheese. He sold millions of pounds of the stuff to the American military during World War I. The technique ultimately led to the creation of Velveeta and a whole universe of processed cheese products.

You can apply the very same chemistry, however, to achieve much higher culinary purposes. The chefs in our research kitchen have made mac and cheese with an intense goat gouda and cheddar sauce, for example, and build gourmet grilled cheese sandwiches using cheese slices that melt like the processed stuff, but are made from feta or Stilton.

In place of sodium phosphate, we use sodium citrate, which is easier to find in grocery stores or online. Like sodium phosphate, sodium citrate is an emulsifying salt that helps tie together the two immiscible components of cheese: oil and water.

In solid form, cheese is a stable emulsion. The tiny droplets of dairy fat are suspended in water and held in place by a net of interlinked proteins. When cheese melts, however, that net breaks apart, and the oil and water tend to go their separate ways. Sodium citrate can form attachments to both fat and water molecules, so it holds everything together. The end result is a perfectly smooth, homogeneous sauce. The sauce even can be cut into processed cheese-like slices once it cools.

When making cheese sauce, we add 4 grams of sodium citrate for every 100 grams of finely grated cheese and 93 grams of water or milk. To make cheese slices, we reduce the amount of water to about 30 grams (cold wheat beer works very well, too), pour the melted mixture into a sheet pan, and let it solidify in the refrigerator for about two hours before cutting it into pieces, which then can be wrapped in plastic and frozen.

Because this method of stabilizing melted cheese bypasses all of the flour, butter and milk used in Mornay sauce, the resulting cheese sauce is much richer; a little goes a long way. But the sauce keeps well in the refrigerator and reheats nicely in the microwave, so save any extra and use it to top vegetables, nachos or pasta.

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MODERNIST MAC AND CHEESE

We've offered both weight and volume measurements for this recipe. But as with most modernist recipes, a digital scale is best. Sodium citrate is widely available online. Feel free to substitute an equal amount of your favorite cheeses in this recipe. If you have an immersion blender, you can use it to blend the cheese sauce instead of transferring it to a food processor. But this can cause splattering, so do so with care.

Start to finish: 30 minutes

Servings: 5

2 cups elbow macaroni

265 milliliters (1 1/8 cups) milk or water

11 grams (2 1/4 teaspoons) sodium citrate

285 grams (about 2 1/2 cups) finely grated white cheddar cheese

Salt, to taste

Bring a large pot of water to a boil. Add the pasta and cook until al dente, 5 to 6 minutes. Drain the pasta, but do not rinse it.

Meanwhile, in a medium saucepan over medium heat, whisk together the milk or water and sodium citrate. Bring to a simmer. Add the cheese, a spoonful at a time, stirring well between additions. Continue stirring until the cheese is melted and steaming, then transfer the sauce to a food processor. Process until completely smooth, about 30 seconds.

Transfer the cheese sauce immediately back to the saucepan, and return to the heat. Once the sauce is hot, add the pasta, and stir until coated. Season with salt.

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EDITOR'S NOTE: Scott Heimendinger is the director of applied research for The Cooking Lab, the culinary research team led by Nathan Myhrvold that produced the cookbooks "Modernist Cuisine: The Art and Science of Cooking" and "Modernist Cuisine at Home."